The worldwide spread of severe acute respiratory syndrome (SARS) raised questions about the risk of importation of such infection, in particular by air travel. Entry screening was implemented in some countries although poor evidence on its effectiveness is reported. We developed a model to estimate the number of imported SARS cases between regions, using the 2003 SARS epidemic data to apply this model for two scenarios: from Beijing to Frankfurt and from Hong Kong to London. We back-calculated the data to estimate individuals' time of infection and built a model where every individual has a probability of being isolated, of traveling, and of being undetected at arrival. The findings, consistent with what was observed in 2003, suggest that entry screening does not affect the predicted number of imported cases. Inversely, importation depends on the transmission dynamic in the country of origin (including control measures in place) and on the intensity of air travel between regions.(R.A.)

OBJECTIVE:
A competent vector of dengue and chikungunya viruses, Aedes albopictus, is present in Europe. As a first step towards assessing the likelihood of local transmission of these viruses in Europe, we estimated the number of viremic person-days among air-travellers arriving in the European Union (EU).
METHODS:
For dengue, we developed a Monte Carlo model with the following parameters: probability distributions based on quarterly incidences in endemic countries (years 2003-2007), passenger flow from endemic to EU countries (year 2006), duration of viremia, probability of being viremic upon arrival, distribution and period of vector activity in the EU. For chikungunya, due to scarce incidence data, we developed a model with point estimates.
RESULTS:
We estimated at 4763 (range 3067-7019) the median dengue viremic person-days in 2006 with highest estimate among travellers from Asia during the third quarter. Dengue estimates among travellers arriving in EU Aedes-infested areas from April to October were 169 viremic person-days, 130 arriving in Italy. For chikungunya, we estimated 6 viremic person-days in EU Aedes-infested areas among air-travellers from India; all occurred in Italy.
CONCLUSION:
Our results are a first step towards a real estimation of the risk of local dengue transmission in Europe. Further research is needed to better understand vector capacity and other factors related to virus transmission in temperate climates. Information on personal protection to travellers, early diagnosis and implementation of vector monitoring and control should be a priority in EU areas where the vector is established.